The combustion chamber of a gas turbine is exposed to particular loads, for example hot gases or vibrations. For this reason so-called heat shields are mounted on the support structure to protect the support structure from the hot gases and other loads.
Heat shields in a combustion chamber, in particular metal heat shields, are attached to the support structure with a screw. So-called cup-spring assemblies are used here for attachment purposes. Metal heat shield plates are fastened in a central manner using the cup-spring assemblies. The cup-spring assembly consists of a sleeve and cup springs arranged in the sleeve. These have a continuous axial hole on the inside. The cup-spring assemblies have a thread on parts of the axial hole. The screw is screwed into this axial hole. An external thread is positioned on the outside of the cup-spring assemblies, in other words on the sleeve. This is used to screw the cup-spring assembly into the support structure. A recess with a suitable internal thread is provided in the support structure for this purpose. The screw head is then arranged in or on the heat shield. Screwing the screw into the recess fastens the heat shield to the support structure. The screw here can be such that it projects through the cup-spring assembly screwed into the support structure, thereby extending further into the recess in the support structure.
In the direction of the combustion chamber the sleeve has a permanently attached cover, which can also have an axial hole to accommodate the screw. The cover is as it were part of the sleeve. The cup springs therefore do not fall into the combustion chamber. The cup springs of the cup-spring assembly are secured on the side in the direction of the support structure with a securing ring to prevent them falling out. A pressure plate is also arranged between the security ring and the spring. However in the past the security ring has quite often come loose or has fractured. If a heat shield then has to be taken down/mounted due to cracks or fractures, if the security ring is fractured, the springs and pressure plate can themselves fall into the combustion chamber. These must then be located and removed in a time-consuming operation. The mounting of new cup-spring assemblies is also difficult, as the rear face of the support structure is not accessible from the outside at some points, for example at the hub.